1. Preheat your oven to 350°F (175°C). Grease a 9×5-inch loaf pan and line it with parchment paper.

2. Grate the zucchini and squeeze out excess moisture using a towel. Peel, core, and finely chop the apple.

3. In a large mixing bowl, beat together melted butter, granulated sugar, and brown sugar. Add eggs and vanilla extract, and mix until smooth.

4. Stir in flour, baking soda, salt, and cinnamon until just combined.

5. Fold in the zucchini and chopped apple.

6. Pour the batter into the prepared pan and smooth the top.

7. Bake for 50–60 minutes, or until a toothpick inserted in the center comes out clean. Let cool 10 minutes in the pan, then transfer to a wire rack.

8. For the frosting: In a saucepan, melt 1/4 cup butter and stir in 1/2 cup brown sugar. Cook for 1–2 minutes until bubbling.

9. Remove from heat, add milk and vanilla, whisk until smooth. Stir in powdered sugar until glossy.

10. Pour warm frosting over the cooled loaf and let it set before slicing.